1. Field of the Invention
Embodiments of the present invention relate generally to devices for performing measurements on small quantities of gases or liquids, and particularly to an apparatus for performing gas sorption measurements on multiple samples of gases.
2. Description of the Related Art
Synthesis of materials using combinatorial chemistry has been used effectively to produce new materials having small variations in composition and/or structure numbering in the 10s, 100s or 1000s at a time. Such materials processing methods have led to the discovery of new and improved chemicals, pharmaceuticals, semiconductor materials and devices. However, due to the large numbers of different materials involved, combinatorial methods can only lead to timely material discovery when rapid screening of the physical characteristics of the many types of new materials produced thereby is available.
In the case of gas sorption materials, the gas sorption properties of each new material must be tested, i.e., the absorption, adsorption, desorption, physisorption, and/or chemisorption properties, and such testing for even a single sample is a lengthy and labor-intensive process. Specifically, an extensive battery of tests is conducted in which the quantity of a dosing gas that can be contained by the material is characterized at different temperatures and pressures. A sample of the material in question is held in a chamber and is either dosed with a known quantity of a dosing gas, e.g., hydrogen, or a known quantity of the dosing gas is removed from the chamber. Typically, the chamber is maintained at a constant temperature and the chamber pressure increases or decreases as dosing gas flows into or out of the material sample. The pressure in the chamber is recorded with respect to time, and a pressure-composition-temperature (PCT) curve is established for the material from the equilibrium pressures obtained with every dose of gas. Once an equilibrium state is reached for an individual dose of gas in the chamber, i.e. the absorption/desorption rate of the dosing gas approximates zero, the equilibrium pressure for the sample material at the given experimental temperature is known. Because the chamber has a known volume and temperature, the total quantity of dosing gas that has sorbed into or desorbed out of the sample material can be calculated using the ideal gas law. The absorption or desorption test is then repeated at a different pressure-higher for absorption characterization and lower for desorption characterization-until a PCT curve is generated for the sample material from the equilibrium pressures and concentrations collected from a sequence of gas doses.
The sorption tests for establishing each PCT curve are time-consuming and require very sensitive instrumentation, such as high-accuracy pressure transducers. Thus, characterizing the sorption properties of a new material is a relatively expensive and lengthy process, especially since current testing techniques do not allow rapid screening or testing across multiple samples. In light of the expanding need for characterizing large numbers of new materials, current techniques simply cannot be used to efficiently or cost effectively analyze the large numbers of different materials to be tested.
Accordingly, there is a need in the art for a technique for efficiently and accurately performing gas sorption measurements on a large number of samples. 